The present invention relates to improvements in sunlamps and to improvements in sources of ultraviolet radiation which can be used in sunlamps.
My U.S. Pat. No. 4,095,113 (the disclosure of this patent is incorporated herein by reference) describes a sunlamp which can employ a substantial number (e.g., between 5 and 20) discrete elongated sources of ultraviolet radiation. The sources are parallel to each other and their envelopes preferably constitute filters which intercept radiation except in the so-called UVA region and preferably also in the upper part of the so-called UVB region. The envelopes can be filled with mercury vapors and their internal surfaces may be coated with a layer or film of radiation producing material in a manner as disclosed in the aforesaid patent. The arrangement is such that the sources cooperate with reflector means (e.g., of the type disclosed in my U.S. Pat. No. 4,106,083 granted Aug. 8, 1978) to establish a high-density radiation field close to the exit opening or openings of the reflector means. A person desirous of rapidly acquiring a tan places his or her body or a selected portion of the body into close proximity of the opening or openings.
It is advisable to insure that radiation sources which are utilized in a sunlamp (e.g., a sunlamp of the type disclosed in the aforesaid patent) cannot be used in other types of lamps, for example, in lamps whose fixtures can accept standard sources of fluorescent light. This will be readily appreciated since excessive exposure of persons occupying the area which is illuminated by one or more sources of ultraviolet radiation could cause sunburn or other undesirable effects. It is equally desirable to insure that a sunlamp be designed in such a way that it cannot accept standard sources of fluorescent light, i.e., light sources (such as neon lamps) which are not designed to emit ultraviolet radiation. For example, a person desirous of acquiring a tan could be exposed to radiation issuing from tubular light sources of the type customarily employed in the field of photography; exposure to radiation issuing from such sources could be harmful to the person who expects to acquire a tan.
One of the solutions which appear to be close at hand is to equip the sunlamps with special sockets which are designed in such a way that they cannot accept the contacts and/or plugs of conventional radiation sources, i.e, of sources other than those which are specifically designed to emit radiation in the ultraviolet region. For example, it is possible to replace pairs of standard electric contacts at each end of an elongated tubular radiation source with a single oval projection having two terminals embedded therein and to equip the housing of the sunlamp with special sockets which can accept such oval projections. The just discussed light sources and sockets therefor are available on the market; however, they are used only in connection with light sources whose tubular envelopes have a diameter of approximately 40 mm.
Many tubular light sources whose light output is relatively low comprise envelopes with an outer diameter of approximately 25 mm. As a rule, the length of such tubular light sources is 437.4 mm (according to US Standard C 78.404-1964). The end portions of these light sources carry plugs with pairs of standard pin-shaped electric contacts which are removably insertable into complementary sockets. A light source which is designed to emit ultraviolet radiation in the UVA region (and perhaps in the upper part of the UVB region) and which has the just mentioned dimensions could be readily inserted into the sockets of standard light fixtures which is undesirable for the aforementioned reasons. A modification of the sockets and plugs (including the prongs) is not economical in view of the relatively small number of such sources of ultraviolet radiation (especially when compared with the number of radiation sources whose outer diameter is approximately 40 mm). Therefore, the provision of sources of ultraviolet light having an outer diameter of approximately 25 mm and a length of 437.4 mm with specially designed plugs, prongs or projections and sockets would contribute excessively to the initial cost of such commodities.